SEPTEMBER 6, 2011

Analysis: Assessing the impact of KERS

KERS (Kinetic Energy Recovery Systems) were first used in F1 in 2009, abandoned the following season and reintroduced this year, at the same output levels as the original systems.

While the impact of the new DRS (Drag Reduction System) has attracted much attention this year, Mercedes believes that KERS has played a key role in increased overtaking, in association with DRS. KERS has been used variously to boost drivers into the ‘DRS zone’ (i.e. less than one second behind the car in front), during overtaking itself, or to defend against a car behind with DRS in operation. Anecdotal evidence suggests KERS plays a role in nearly every overtaking move for cars that have the system, as well as providing a valuable area of cutting-edge research into electronics and battery technology.

Q: How does the Mercedes-Benz KERS work?

It has been developed by Mercedes-Benz High Performance Engines in Brixworth, UK, with the support of Mercedes-Benz R&D in Sindelfingen, Germany - a process that also resulted in significant knowledge transfer to series production of hybrid technology. The KERS is made up of the Motor

Generator Unit (MGU), the Power Electronics (PE) and a number of batteries that make up the Energy Storage System (ESS). When harvesting power that would otherwise be dissipated as heat through the braking system, the MGU works as a generator, providing three-phase electricity to the PE. This converts the electricity to DC voltage and stores the energy in the battery. The process works in reverse when the driver requests boost, the generator unit becoming a motor to supplement engine power. The processes of harvesting and boosting are both approximately 80% efficient.

Q: How large is the Mercedes-Benz KERS?

The motor in the MGU is approximately ten times smaller than commercial automotive units, while the battery is around eight times smaller than those commercially available. Overall, there are approximately 3,500 parts in a single KERS!

Q: What is the lap time benefit of KERS at Monza?

With full use of KERS it is over 0.4s at Monza, compared to a lowest value so far this season of approximately 0.3s per lap in Hungary.

Q: Why is KERS so potent at Monza?

The best-case scenario for KERS boosting is relatively slow corners followed by very long straights - exactly what Monza features.

There are four times in the lap (out of Turns 2, 7, 10 and 11) when the car accelerates from relatively low speed to near terminal velocity, and this means a relatively large lap-time benefit from boosting out of any of these four corners. Typical KERS deployment in Monza would see four boosts per lap, which are delivered to the wheels 20 milliseconds after the button is pressed.

Q: Monza also features heavy braking. Does that make it a good circuit for harvesting energy?

The cars spend over 12% of the lap (more than 10 seconds) on the brakes in Monza. Braking for Turn 1, they shed around 165mph. However, Monza is actually the most marginal circuit of the year for KERS harvesting, owing to the low number of braking areas during the lap: just six in total (Turns 1, 4, 6, 7, 8 and 11).